(a) Field of the Invention
The present invention relates to a display device and a manufacturing method thereof, and more particularly, to a display device including an organic thin film transistor (OTFT) and a manufacturing method thereof.
(b) Description of Related Art
Among various display devices, the flat display device with its small and lightweight characteristics has recently become more prominent. A liquid crystal display (LCD), such as an organic light emitting diode (OLED) device or the like, is used as such a flat display device and includes at least one thin film transistor to realize an image. The thin film transistor (TFT), which is a switching or driving device for controlling or driving an operation of each pixel, respectively, comprises a gate electrode, a gate insulating film covering the gate electrode and a semiconductor layer positioned on the gate insulating film. Here, the semiconductor layer uses amorphous silicon or poly silicon, and applications of an organic semiconductor have recently increased.
Because the organic semiconductor (OSC) may be formed under normal temperature and pressure, there is an advantage in that manufacturing cost can be reduced, and the OSC can be applied to a thermally weak plastic substrate. Such an OSC may be formed through a simple ink jet method without complicated processes of coating, light exposing and developing and the like. In order to form the OSC through the ink jet method, a barrier wall having an opening for exposing a region (channel region) at which the OSC will be positioned is formed, and an organic semiconductor solution is jetted into the opening, then a process of removing a solvent is used so that an OSC layer is formed.
Because a TFT including an organic semiconductor layer is typically a very small device, it is difficult to control an organic semiconductor solution to be jetted precisely into an opening. Therefore, there may be a problem in that the jetted organic semiconductor solution may be positioned on a barrier wall, and thus the thickness of the organic semiconductor layer becomes different for each pixel so that each organic TFT shows a different characteristic. To solve such a problem, a surface treatment is executed on a barrier wall such that the organic semiconductor solution is flowed into the opening. Through the surface treatment, the surface of the barrier wall has water and oil repellency, and the organic semiconductor solution positioned on the barrier wall is flowed into a closed space. Meanwhile, there is a problem in that a property of a gate insulating film positioned beneath the bottom of the organic semiconductor layer may be changed, and thus the characteristic of the organic TFT may be degraded.